The cerebral cortex encompasses several major regions that are involved in higher functions such as thought, feelings, memory and planning (Principles of Neural science, 2nd Edition, Elsevier Science Publishing co., Inc. 1985, pp 671-687). Biogenic amines, i.e. dopamine, norepinephrine and serotonin, are important for mammalian cortical function. The ascending dopamine and norepinephrine pathways innervate the cortex. The serotonergic neurons of the CNS project to virtually all regions of the brain including the cerebral cortex (Fundamental Neuroscience, Academic press 1999, pp 207-212). Primary or secondary dysfunctions in the activity of these pathways lead to dysregulation of the activity at dopamine and norepinephrine and serotonin receptors in these brain areas and subsequently to manifestations of psychiatric and neurological symptoms.
The biogenic amines of the cortex modulate several aspects of cortical functions controlling affect, anxiety, motivation, cognition, attention, arousal and wakefulness (Neuropsychopharmacology, 5th generation of Progress, Lippincott, Williams and Wilkins 2002, Chapter 34). Thus, the catecholamines dopamine and norepinephrine exert strong influence on the prefrontal cortical areas, the integrity of which is essential for the so-called executive cognitive functions, related to e.g. attention, planning of actions and impulse control (the role of the catecholamines in these respects is reviewed in Arnsten and Li, 2005, Biol Psychiatry; 57; 1377-1384). Norepinephrine is a major part in the circuitry regulating anxiety and fear and is thus believed to be dysregulated in anxiety disorders such as panic disorders, generalized anxiety disorder (GAD) and specific phobias (Sullivan et al. 1999, Biol Psychiatry; 46:1205-121). Concerning mood and affective functions, the usefulness of compounds facilitating particularly norepinephrine and serotonin neurotransmission in the treatment of depression and anxiety has strongly contributed to the widely-accepted concept that these neurotransmitters are both involved in the regulation of affective functions (Goodman & Gilman's The Pharmacological Basis of Therapeutics, Tenth Edition, McGraw-Hill, 2001).
In general, compounds specifically affecting the transmission of biogenic amines, more precisely monoamines, norepinephrine, dopamine and serotonin are successfully used to alleviate the affective, cognitive, or attentional symptoms in patients suffering from e.g. depression, anxiety and attention deficit hyperactivity disorders (ADHD).
Furthermore, the monoamine systems in the cortex are known to be directly or indirectly involved in the core symptoms of schizophrenia. Based on a synthesis of biochemical and genetic findings along with neuropsychological observations indicating dysfunction of specific cortical areas in schizophrenia, it has been proposed that this disorder emerges as various pathological etiologies converge upon cortical function leading to dysregulation of the cortical micro-circuitry, which is clinically manifested as the symptoms of schizophrenia (Harrison and Weinberger, 2005, Molecular Psychiatry; 10:40-68). This cortical micro-circuitry is regulated by several neurotransmitters, including glutamate, GABA, and dopamine.